The invention relates to a drawbar-type rear wheel suspension for motor vehicles comprising a drawbar axle body which is mounted to the vehicle body by means of a universal joint and which has vehicle wheel support arms engaged at their free ends by struts which extend in a transverse plane of the vehicle. The universal joint is disposed at a lower level than the strut joints supporting the drawbar arms. Each strut is supported on the vehicle body by an elastic pivot joint, which is disposed at a higher level than the strut joints with the drawbar arms. The drawbar axle body is elastically deformable at least in a direction transverse to the vehicle.
Such a drawbar-type wheel suspension is known for example from EP 0 811 512 A1. In the area of the drawbar body pivot joint, the drawbar body is either pivotable or elastically bendable. A deformation of the drawbar about a pivot joint or a bendable area however results in a relatively large wheel displacement in the travel direction particularly during upward movement of both wheels. This wheel displacement causes undesired jerking motions particularly in lightweight compact cars.
A drawbar-type wheel suspension with struts interconnecting the trailing ends of the drawbar body is further known from DE 44 22 875 A1. In this case, the struts are two curved rods, which extend essentially in parallel relationship and are joined at their inner ends thereby forming a double-sided triangular transversal swing arm (A-arm). The double A-arm has its outer opposite ends pivotally connected to the trailing arm ends of the drawbar axle body behind the wheel center cross-sectional plane. In the center area, the struts are supported on the vehicle body in a statically defined manner by a pivot support member which is pivotable about a transverse vehicle axis. During upward and downward movement of the wheels the lever arrangement formed by the double A-arms and the pivot support member performs a scissors-like movement. Because of the many joints in the lever arrangement, there is a relatively low transverse rigidity which does not provide for firm side force support and/or does not permit good roll and/or side force control or it makes such control possible only with relatively expensive additional structures.
It is the object of the present invention to provide a rear axle for a vehicle with drawbar-type wheel suspension which has positive roll and/or side force control properties and which can be manufactured and installed easily and inexpensively and which furthermore requires only a minimum amount of struts and joints.
In a drawbar-type rear wheel suspension for a motor vehicle comprising a drawbar axle body connected to the vehicle body by a universal drawbar body joint and having wheel support arms on which vehicle wheels are supported, and struts extending laterally between the free ends of the wheel support arms and the vehicle body and being connected thereto by elastic pivot joints, the elastic pivot joints of the struts at the vehicle body are disposed at a higher level than the universal drawbar joint and also the elastic pivot joints of the struts at the wheel support arms, and further, the drawbar axle body has a uniform cross-section over its full length and provides for an elasticity such that the deformation of the drawbar axle caused by side forces is in the same range as the sum of the deformations of the elastic pivot joints of at least one strut.
The vehicle supports the trailing arm axle body by way of maximally three joints. It is possible that the struts are connected to a joint pin, which is mounted to the vehicle body whereby the trailing arm axle body is connected to the vehicle body only by way of two joints.
The number of joints for the trailing arm wheel suspension altogether, however, is limited to five; the four joints at the ends of the struts and the trailing arm axle body joint. The four strut joints may be, dependent on the wheel suspension design, pivot or ball joints, notwithstanding their elastic liners. The smaller number of joints provides for a stiff suspension structure.
The trailing arm axle body, which may have an open or closed cross-section, is designed to be elastic. On one hand, the elastic deformability has the advantage that, upon upward movement of the wheels, the trailing arm axle body accommodates the change of the wheelbase caused by the pivot movement of the struts. On the other hand, the wall thickness of the axle body may be small in comparison with the usual De-Dion axle without any detrimental effects on the side force support capability. This is because the struts connected to the center area of the wheels transmit the side forces, which are effective when the vehicle negotiates a curve, directly to the vehicle body.
The invention will be described below in greater detail with reference to a particular embodiment of the invention which is schematically represented in the accompanying drawings.